1. Field of Invention
This invention relates generally to blind fasteners of the toggle bolt type which are insertable in a hole drilled in a hollow wall, and more particularly to a toggle bolt assembly including means that act to prevent rotation of the toggle in the course of installation when the bolt is turned to axially advance the toggle into engagement with the inner surface of the wall to fasten the assembly thereon.
2. Prior Art
Blind fasteners of the toggle bolt type are commonly used to secure fixtures and other objects against the outer surface of a hollow wall formed of masonry, tile, cinder block, plaster or fiber board, or any other plate or panel capable of supporting a load.
Webster's Third New International Dictionary defines a toggle as "a piece or device for holding or securing." As used herein, the term "toggle bolt" refers to a blind fastener having a collapsible toggle threadably received on the shank of a bolt whereby when the bolt is passed through a hole in a wall, the toggle is then collapsed to permit such passage; and when emerging from the hole, the toggle resumes its non-collapsed form to effect a fastening action. By a collapsible toggle is meant any holding element that is foldable, bendable, compressible or otherwise changeable to assume in the collapsed state reduced dimensions to permit its passage through a hole.
The most commonly known toggle bolt consists of a threaded bolt or screw on which is received a nut provided with opposed lugs or trunnions to pivotally support a pair of spring-biased wings. The wings, which are normally outstretched, fold in against the bolt when it is inserted in a drilled hole in the wall, the hole diameter being large enough to accommodate the folded-in wings. Toggle bolts of this conventional type are available in various sizes and weights, depending on the loads they are intended to support on a wall.
When installing a conventional toggle bolt in a hollow wall to hold a fixture or other object against its outer surface, a hole is first drilled in the wall, the diameter of the hole depending on the gauge of the toggle bolt. The toggle bolt assembly is inserted through a mounting hole in the fixture and pushed into the wall hole, the wings folding in to permit such entry. The length of the bolt is greater than the combined thickness of the fixture, the wall and the folded-in toggle wings. Hence, the wings pivoted on the nut, which is initially near the end of the bolt, resume their outstretched state when the bolt is fully inserted. The outstretched wings are thus displaced a substantial distance from the inner surface of the wall. The extent of this displacement depends on the length of the bolt relative to said combined thickness.
It is not at this point possible to tighten the wall-inserted toggle bolt; for should one turn the screw with a screw driver, the wings, which are free, will also turn and the trunnion nut will not advance on the screw toward the inner surface of the wall. In order, therefore, to effect tightening with a conventional toggle bolt, the installer must pull the fixture away from the wall to cause the outstretched wings to engage the inner surface of the wall and thereby resist a turning action. In this way, the screw can be turned with a screw driver without at the same time turning the wings, and the nut will then advance on the screw to effect tightening of the toggle bolt.
In practice, the need to manually pull the fixture away from the wall in order to tighten the toggle bolt will in many instances present serious difficulties. For example, if panels of insulation material are to be fastened to a hollow roof by means of roofing plates, the installer for each such plate must insert the toggle bolt through a mounting hole in the plate and thread the screw into the trunnion nut. A hole in the insulation panel and a hole in the roof are then made. The screw carrying the toggle wings is inserted through the panel and roof holes; and the wings then assume their outstretched state at a position displaced from the inner surface of the roof.
In order to now tighten the anchor bolt, the installer must place his fingers beneath the roofing plate so as to pull the roofing plate away from the insulation panel lying on the roof until the wings then engage the inner surface of the roof, thereby preventing rotation of the wings to permit tightening of the toggle bolt.
Most professional installers now use electric screw drivers which to be rendered operative must be pressed against the head of the screw. This presents no difficulty when the screw head lies against a stable substrate. But if the head of the screw lies against a roofing plate being held in one hand by the installer while his other hand holds the electric screw driver, the inherent instability of the situation makes installations very difficult and dangerous.
One must bear in mind that a professional installer is required in the case of a typical roof installation to put in thousands of toggle bolts, and that with conventional toggle bolts, the need to pull up the roofing plate in order to tighten the bolt not only adds significantly to the time it takes to make the installation, but also increases the risk of crushed fingers or other mishap.
Moreover, in a roof installation in which the insulation panels are secured by toggle bolts, the toggle bolts are vertically disposed; and since the exposed roof is subject to vibratory and compressive forces, this causes the toggle wings to actually unscrew to a point where the wings will fall off the screw, thereby leaving the insulation panels unsecured. As a consequence, the panels may be blown off the roof in a high wind producing a strong updraft.
The following patents which deal with various forms of toggle bolts are of background interest:
Pleister--U.S. Pat. No. 2,061,634 PA1 Gelpcke--U.S. Pat. No. 2,398,220 PA1 Shamah--U.S. Pat. No. 4,286,497 PA1 Apelzweig--U.S. Pat. No. 2,998,743 PA1 Gelpcke--U.S. Pat. No. 2,567,372 PA1 Zifferer--U.S. Pat. No. 1,228,512 PA1 Goewey--U.S. Pat. No. 1,373,188 PA1 Brenizer--U.S. Pat. No. 1,600,034 PA1 Karitzky--U.S. Pat. No. 2,616,327 PA1 Topf--U.S. Pat. No. 3,302,508 PA1 Vaillancourt--U.S. Pat. No. 3,389,631 PA1 Forsberg--U.S. Pat. No. 3,513,746 PA1 Roberson--U.S. Pat. No. 4,079,655 PA1 Shamah--U.S. Pat. No. 4,286,497 PA1 Schrandolph--No. 1,237,386 (Fed. Rep. Ger.)